Sebastian Ivens

Lasting Blood-Brain Barrier Disruption Induces Epileptic Focus in the Rat Somatosensory Cortex

Perturbations in the integrity of the blood-brain barrier have been reported in both humans and animals under numerous pathological conditions. Although the blood-brain barrier prevents the penetration of many blood constituents into the brain extracellular space, the effect of such perturbations on the brain function and their roles in the pathogenesis of cortical diseases are unknown. In this study we established a model for focal disruption of the blood-brain barrier in the rat cortex by direct application of bile salts. Exposure of the cerebral cortex in vivo to bile salts resulted in long-lasting extravasation of serum albumin to the brain extracellular space and was associated with a prominent activation of astrocytes with no inflammatory response or marked cell loss. Using electrophysiological recordings in brain slices we found that a focus of epileptiform discharges developed within 4-7 d after treatment and could be recorded up to 49 d postoperatively in >60% of slices from treated animals but only rarely (10%) in sham-operated controls. Epileptiform activity involved both glutamatergic and GABAergic neurotransmission. Epileptiform activity was also induced by direct cortical application of native serum, denatured serum, or albumin-containing solution. In contrast, perfusion with serum-adapted electrolyte solution did not induce abnormal activity, thereby suggesting that the exposure of the serum-devoid brain environment to serum proteins underlies epileptogenesis in the blood-brain barrier-disrupted cortex. Although many neuropathologies entail a compromised blood-brain barrier, this is the first direct evidence that it may have a role in the pathogenesis of focal cortical epilepsy, a common neurological disease.

Transcriptome Profiling Reveals TGF-β Signaling Involvement in Epileptogenesis

Brain injury may result in the development of epilepsy, one of the most common neurological disorders. We previously demonstrated that albumin is critical in the generation of epilepsy after blood–brain barrier (BBB) compromise. Here, we identify TGF-β pathway activation as the underlying mechanism. We demonstrate that direct activation of the TGF-β pathway by TGF-β1 results in epileptiform activity similar to that after exposure to albumin. Coimmunoprecipitation revealed binding of albumin to TGF-β receptor II, and Smad2 phosphorylation confirmed downstream activation of this pathway. Transcriptome profiling demonstrated similar expression patterns after BBB breakdown, albumin, and TGF-β1 exposure, including modulation of genes associated with the TGF-β pathway, early astrocytic activation, inflammation, and reduced inhibitory transmission. Importantly, TGF-β pathway blockers suppressed most albumin-induced transcriptional changes and prevented the generation of epileptiform activity. Our present data identifies the TGF-β pathway as a novel putative epileptogenic signaling cascade and therapeutic target for the prevention of injury-induced epilepsy.

Astrocytic dysfunction in epileptogenesis: consequence of altered potassium and glutamate homeostasis?

Focal epilepsy often develops following traumatic, ischemic, or infectious brain injury. While the electrical activity of the epileptic brain is well characterized, the mechanisms underlying epileptogenesis are poorly understood. We have recently shown that in the rat neocortex, long-lasting breakdown of the blood–brain barrier (BBB) or direct exposure of the neocortex to serum-derived albumin leads to rapid upregulation of the astrocytic marker GFAP (glial fibrillary acidic protein), followed by delayed (within 4–7 d) development of an epileptic focus. We investigated the role of astrocytes in epileptogenesis in the BBB-breakdown and albumin models of epileptogenesis. We found similar, robust changes in astrocytic gene expression in the neocortex within hours following treatment with deoxycholic acid (BBB breakdown) or albumin. These changes predict reduced clearance capacity for both extracellular glutamate and potassium. Electrophysiological recordings in vitro confirmed the reduced clearance of activity-dependent accumulation of both potassium and glutamate 24 h following exposure to albumin. We used a NEURON model to simulate the consequences of reduced astrocytic uptake of potassium and glutamate on EPSPs. The model predicted that the accumulation of glutamate is associated with frequency-dependent (>100 Hz) decreased facilitation of EPSPs, while potassium accumulation leads to frequency-dependent (10–50 Hz) and NMDA-dependent synaptic facilitation. In vitro electrophysiological recordings during epileptogenesis confirmed frequency-dependent synaptic facilitation leading to seizure-like activity. Our data indicate a transcription-mediated astrocytic transformation early during epileptogenesis. We suggest that the resulting reduction in the clearance of extracellular potassium underlies frequency-dependent neuronal hyperexcitability and network synchronization.

Acetylcholine-induced seizure-like activity and modified cholinergic gene expression in chronically epileptic rats

The entorhinal cortex (EC) plays an important role in temporal lobe epilepsy. Under normal conditions, the enriched cholinergic innervation of the EC modulates local synchronized oscillatory activity; however, its role in epilepsy is unknown. Enhanced neuronal activation has been shown to induce transcriptional changes of key cholinergic genes and thus alter cholinergic responses. To examine cholinergic modulations in epileptic tissue we studied molecular and electrophysiological cholinergic responses in the EC of chronically epileptic rats following exposure to pilocarpine or kainic acid. We confirmed that while the total activity of the acetylcholine (ACh)‐hydrolysing enzyme, acetylcholinesterase (AChE) was not altered, epileptic rats showed alternative splicing of AChE pre‐mRNA transcripts, accompanied by a shift from membrane‐bound AChE tetramers to soluble monomers. This was associated with increased sensitivity to ACh application: thus, in control rats, ACh (10–100 µm) induced slow (< 1Hz), periodic events confined to the EC; however, in epileptic rats, ACh evoked seconds‐long seizure‐like events with initial appearance in the EC, and frequent propagation to neighbouring cortical regions. ACh‐induced seizure‐like events could be completely blocked by the non‐specific muscarinic antagonist, atropine, and were partially blocked by the muscarinic‐1 receptor antagonist, pirenzepine; but were not affected by the non‐specific nicotinic antagonist, mecamylamine. Epileptic rats presented reduced transcript levels of muscarinic receptors with no evidence of mRNA editing or altered mRNA levels for nicotinic ACh receptors. Our findings suggest that altered cholinergic modulation may initiate seizure events in the epileptic temporal cortex.

Prescription patterns of patients diagnosed with schizophrenia in mental hospitals in Tashkent/Uzbekistan and in four German cities

Little is known about psychopharmacological prescription practice in low‐income countries. The present study aimed for an analysis of pharmacological treatment strategies for inpatients with schizophrenia in Tashkent, the capital city of Uzbekistan, facing a low‐income situation as compared with four German cities in a high‐income Western situation.

Elucidating the Complex Interactions between Stress and Epileptogenic Pathways.

Clinical and experimental data suggest that stress contributes to the pathology of epilepsy. We review mechanisms by which stress, primarily via stress hormones, may exacerbate epilepsy, focusing on the intersection between stress-induced pathways and the progression of pathological events that occur before, during, and after the onset of epileptogenesis. In addition to this temporal nuance, we discuss other complexities in stress-epilepsy interactions, including the role of blood-brain barrier dysfunction, neuron-glia interactions, and inflammatory/cytokine pathways that may be protective or damaging depending on context. We advocate the use of global analytical tools, such as microarray, in support of a shift away from a narrow focus on seizures and towards profiling the complex, early process of epileptogenesis, in which multiple pathways may interact to dictate the ultimate onset of chronic, recurring seizures.

Neurobiological consequences of juvenile stress: A GABAergic perspective on risk and resilience

Graphical abstract Figure. No Caption available. HighlightsChildhood stress is an important risk factor for posttraumatic stress disorder.Juvenile stress in rodents models human childhood stress.Juvenile stress induces long‐term alterations in GABAergic neurotransmission.Some GABAergic changes may relate to allostasis rather than behavioral impairments.Behavioral profiling tools allow to dissect resilience‐ and pathology‐related changes. ABSTRACT ALBRECHT, A., MÜLLER, I., ARDI, Z., ÇALIŞKAN, G., GRUBER, D., IVENS, S., SEGAL, M., BEHR, J., HEINEMANN, U., STORK, O., and RICHTER‐LEVIN, G. Neurobiological consequences of juvenile stress: A GABAergic perspective on risk and resilience. NEUROSCI BIOBEHAV REV XXX‐XXX, 2016. – Childhood adversity is among the most potent risk factors for developing mood and anxiety disorders later in life. Therefore, understanding how stress during childhood shapes and rewires the brain may optimize preventive and therapeutic strategies for these disorders. To this end, animal models of stress exposure in rodents during their post‐weaning and pre‐pubertal life phase have been developed. Such ‘juvenile stress’ has a long‐lasting impact on mood and anxiety‐like behavior and on stress coping in adulthood, accompanied by alterations of the GABAergic system within core regions for the stress processing such as the amygdala, prefrontal cortex and hippocampus. While many regionally diverse molecular and electrophysiological changes are observed, not all of them correlate with juvenile stress‐induced behavioral disturbances. It rather seems that certain juvenile stress‐induced alterations reflect the system’s attempts to maintain homeostasis and thus promote stress resilience. Analysis tools such as individual behavioral profiling may allow the association of behavioral and neurobiological alterations more clearly and the dissection of alterations related to the pathology from those related to resilience.

Use of psychiatric inpatient capacities and diagnostic practice in Tashkent/Uzbekistan as compared to Berlin/Germany

ObjectivesThe present study shows a comparison of diagnoses used for the treatment of urban psychiatric inpatients in Tashkent/Uzbekistan and Berlin/Germany. Differential diagnostic practices related to different traditions in psychopathology between the two settings are analysed to explain part of the difference in relative frequencies of the diagnoses.MethodsWe conducted a cross-sectional survey of diagnoses used for the treatment of 845 inpatients including 17 out of 18 wards of the Tashkent psychiatric hospital and of all 2,260 psychiatric and psychotherapeutic inpatients in Berlin in October 2008. Relative frequencies of diagnostic categories were calculated for each setting and compared between the two settings using the Chi-square test. A descriptive analysis of differential diagnostic practice is used to explain differences in relative frequencies.ResultsPatients diagnosed with schizophrenia (59.3 vs. 21.0%), with organic mental disorders (20.5 vs. 8.3%), with mental retardation (6.9 vs. 0.2%) and with neurasthenia (1.4 vs. 0.0%) had larger relative frequencies of the psychiatric inpatient population in Tashkent than in Berlin. Patients diagnosed with unipolar depression (24.1 vs. 0.9%), substance use disorder (17.4 vs. 6.4%), adjustment disorder (6.0 vs. 0.4%), schizoaffective disorder (4.9 vs. 0.0%), mania and bipolar disorder (5.3 vs. 0.4%), personality disorder (3.2 vs. 2.0%) and anxiety disorder (3.1 vs. 0.1%) had larger relative frequencies in Berlin than in Tashkent. The diagnostic concept of schizophrenia in Tashkent includes patients with affective psychoses, schizoaffective psychoses and delusional disorders. In Tashkent, mental disorders are more readily associated with organic brain disease such as head trauma or vascular disease than in Berlin.ConclusionsIn Tashkent, most of the psychiatric inpatient capacities are used for the treatment of schizophrenia and organic mental disorders, whereas in Berlin patients with affective disorders, schizophrenia and substance use disorders are most commonly treated as inpatients. The differences can in part be explained by differential diagnostic traditions between the Russian/post-Soviet nosology and the use of the ICD.

Psychometric Properties of a Russian Version of the General Health Questionnaire-28

Background: The 28-item General Health Questionnaire (GHQ-28) is a scaled version of the General Health Questionnaire that has been used internationally to screen for mental disorders in nonpsychiatric populations. There is great need to validate international screening instruments in the Russian language for their use in post-Soviet countries. Methods: 200 persons were surveyed in a deprived area of Almaty, Kazakhstan using the Russian version of the GHQ-28 and socioeconomic measures (income level, employment situation and education). We calculated the median and the mean GHQ-28 scores for different socioeconomic subgroups. The internal reliability was tested using Cronbach’s α coefficient and intersubscale correlations. We conducted an exploratory factor analysis using varimax rotation. Results: The median score of the GHQ-28 was 2 (mean = 3.56; SD = 5.09) for the total sample. Higher age, unemployment and female gender were significantly associated with high mean GHQ-28 scores. Cronbach’s α coefficient was 0.92 for the total scale. Exploratory factor analysis revealed four factors explaining 50.07% of the variance. The factor Anxiety/Insomnia accounted for 14.87%, Severe Depression for 13.74%, Social Dysfunction for 13.47% and Somatic Symptoms for 8.81% of the variance. Conclusions: The test showed good internal consistency. The median GHQ-28 score was relatively low compared to other countries. The subscale Severe Depression including items on suicidal ideation may have a lower acceptance than the other subscales Somatic Symptoms, Anxiety/Insomnia and Social Dysfunction.

Shifts in excitatory/inhibitory balance by juvenile stress: A role for neuron-astrocyte interaction in the dentate gyrus.

Childhood trauma is a well‐described risk factor for the development of stress‐related psychopathology such as posttraumatic stress disorder or depression later in life. Childhood adversity can be modeled in rodents by juvenile stress (JS) protocols, resulting in impaired coping with stressful challenges in adulthood. In the current study, we investigated the long‐lasting impact of JS on the expression of molecular factors for glutamate and γ‐aminobutyric acid (GABA) uptake and turnover in sublayers of the dentate gyrus (DG) using laser microdissection and quantitative real‐time polymerase chain reaction. We observed reduced mRNA expression levels after JS for factors mediating astrocytic glutamate and GABA uptake and degradation. These alterations were prominently observed in the dorsal but not ventral DG granule cell layer, indicating a lasting change in astrocytic GABA and glutamate metabolism that may affect dorsal DG network activity. Indeed, we observed increased inhibition and a lack of facilitation in response to paired‐pulse stimulation at short interstimulus intervals in the dorsal DG after JS, while no alterations were evident in basal synaptic transmission or forms of long‐term plasticity. The shift in paired‐pulse response was mimicked by pharmacologically blocking the astrocytic GABA transporter GAT‐3 in naïve animals. Accordingly, reduced expression levels of GAT‐3 were confirmed at the protein level in the dorsal granule cell layer of rats stressed in juvenility. Together, these data demonstrate a lasting shift in the excitatory/inhibitory balance of dorsal DG network activity by JS that appears to be mediated by decreased GABA uptake into astrocytes. GLIA 2016;64:911–922